article unclassified drug steroid prasterone stereochemistry Dehydroepiandrosterone controlled study Animals DHEA drug synthesis epiandrosterone in vitro study 17 oxoandrost 5 en 3beta yl acetate 17,17 ethylendioxyandrost 5 en 3beta ol 3beta,15alpha dihydroxy 5alpha androstan 17 one 3beta,15beta dihydroxy 5alpha androstan 17 one 3beta,16alpha dihydroxy 5alpha androstan 17 one Antiviral Agents Cercopithecus aethiops Vero Cells Virus Replication androstane derivative animal cell antiviral activity conference paper drug structure hydroxyl group nonhuman priority journal synthesis